P0123: Throttle/Pedal Position Sensor/Switch "A" Circuit High
The throttle or pedal position sensor A voltage is above its normal range, as if the throttle were open beyond its limit.
What P0123 means
P0123 is the high voltage partner of P0122. The throttle or pedal position sensor A is reporting a voltage above about 4.5 to 4.8 volts, which is higher than the throttle can physically produce. The usual causes are a failed sensor, a signal wire shorted to a voltage source, or a broken ground wire that lets the signal float up to the reference voltage. RepairPal also lists a dirty or carbon-filled throttle body and torn or jammed floor mats among possible triggers. Since the computer cannot trust the throttle reading, it may raise the idle, cut power or switch to a backup strategy. Shops watch the sensor voltage on a scan tool, then check the ground circuit with a meter while the sensor is plugged in. A ground that reads more than a few tenths of a volt is a red flag. On drive-by-wire cars the fix is often a new throttle body or pedal assembly. Testing first avoids replacing parts the car does not need.
Common symptoms
- Check engine light on
- High or surging idle
- Hesitation during acceleration
- Reduced power or limp mode
- Hard starting
Most common causes
- Faulty throttle position sensor
- Signal wire shorted to voltage
- Open ground circuit at the sensor
- Chafed or corroded wiring
- Dirty or carbon-filled throttle body
What to check yourself first
Inspect the sensor connector and look for a broken ground wire or corroded pin. Check the throttle body for carbon that can hold the plate open. Make sure the gas pedal returns fully when released.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace throttle position sensor | $185-$258 | When the sensor puts out high voltage with good wiring. |
| Replace throttle body | $623-$766 | On cars where the sensor is built into the throttle body. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For a broken ground or short to voltage. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0122 Throttle/Pedal Position Sensor/Switch "A" Circuit Low
- P0120 Throttle/Pedal Position Sensor/Switch "A" Circuit
- P0121 Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance
- P2135 Throttle/Pedal Position Sensor/Switch "A"/"B" Voltage Correlation
- P0507 Idle Air Control System RPM Higher Than Expected